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Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria EBRA-CUP: A METHODS FOR MIGRATION MEASUREMENT OF ACETABULAR COMPONENTS OF THRs IN DIGITAL STANDARD RADIOGRAPHS PETER MAYRHOFER, revisited April 2012

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Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria EBRA INSTALLATIONS OUTSIDE EUROPE San Francisco, US Los Angeles, US New Orleans, US Memphis Arlington, US New York, US Cleveland Ohio, US Ottawa, Canada Montreal, Canada Tokyo (2), Japan Osaka, Japan Adelaide, Australia Melbourne, Australia Shanghai, China EUROPE Belgium (1) Austria (8) Belgium (1) Denmark (5) France (5) Germany (23) Greece (3) Italy (2) Netherlands (1) Norway (1) Sweden (2) Switzerland (5) United Kingdom (13) April 2012: 84 Installations EBRA has become an International Standard.

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Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria EARLY MIGRATION > 1mm IS PREDICTIVE FOR PROSTHETIC LOOSENING! J Bone Joint Surg Br. 1996 May;78(3):422-26. Early migration predicts late aseptic failure of hip sockets. Krismer M, Stockl B, Fischer M, Bauer R, Mayrhofer P, Ogon M. J Bone Joint Surg Br. 1999 Mar;81(2):273-80. The prediction of failure of the stem in THR by measurement of early migration using EBRA-FCA. Einzel-Bild-Roentgen-Analyse- femoral component analysis. Krismer M, Biedermann R, Stockl B, Fischer M, Bauer R, Haid C. EBRA ENABLES QUALITY CONTROL FOR IMPLANT DESIGN & SURGICAL TECHNIQUE

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Migration is only measurable in serial radiographs of the same patient whose position (exterior orientation) is never exactly the same. time mm EBRA requires at least 4 x-rays per series! Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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EBRA-CUP REQUIRES FULL SIZED AP PELVIS RADIOGRAPHS OF SIZE 430 x 350 mm Resolution min. 75dpi digitized with film scanner or retrieved from PACS system including a scale for calibration! Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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EBRA-FCA ALSO ACCEPTS HIP RADIOGRAPHS NOT SHOWING THE WHOLE PELVIS. Resolution min. 75dpi As the image is calibrated by the true head size, no scale is needed. Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria Tip of stem must be visible!

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EBRA RSA 1 standard x-ray per observation no ball markers retrospective studies 2 special x-rays per observation markers required prospective studies Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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EBRA-CUP PARAMETERS x z y cup inclination & anteversion head & cup x-migration y-migration z-migration not possible Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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EXACT INTRINSIC ORIENTATION IS UNKNOWN IN STANDARD X-RAY X-ray focus principal point film plane Focus-film-distance and position of central beam have to be assessed approximatively. Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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EBRA - LANDMARKS film center approximative principal point Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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cup principal point film focus spatial parameter of migration 3D-METHOD EBRA-CUP reference plane reference line Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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ERRORS CAUSED BY CHANGES OF INTRINSIC ORIENTATION Focus variation within cuboid 60 x 110 x 400 mm affects parameters of migration in a magnitude of only 0.01 mm (experimental study based on 78 radiographs) 900mm 1300mm Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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COMPENSATION OF ERRORS by use of an approximative intrinsic orientation bound to pelvic contours (based on study of 78 random x-rays) by use of variable reference planes passing through the x-ray focus Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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EXTRINSIC ORIENTATION VARIES REMARKABLY Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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ERRORS CAUSED BY CHANGES OF EXTERIOR ORIENTATION Rotations of the pelvic bone cause remarkable errors up to 7 mm of simulated migration! Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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COMPENSATION OF ERRORS by use of a comparability strategy which compares radiographs with respect to similar conditions at exposure migration is measured only in pairs of comparable radiographs overlapping trends are weighted and averaged Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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EBRA COMPARABILITY ALGORITHM time migration non comparable x-ray raw data smoothed data Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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ACCURACY TESTS zero migration experiment (27 x-rays) 33 pairs of x-rays taken within 1 month comparison with RSA (T. Ilchman et al.) Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria J Arthroplasty. 1992 Jun;7(2):121-27. Measurement accuracy in acetabular cup migration. A comparison of four radiologic methods versus roentgen stereophotogrammetric analysis. Ilchmann T, Franzen H, Mjoberg B, Wingstrand H.

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EBRA - ACCURACY MIGRATION MEASUREMENT medio-lateral mig:0.8 mm (95% CI) cranial migration:1.0 mm (95% CI) ANGULAR MEASUREMENT cup anteversion:3.3° cup inclination:2.5° Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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EBRA GRAPHICS PROGRAM PRINTER EXCEL Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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